U.S. Pat. No. 5,595,834 describes a cylindrical stack of cells in which the movement of an air stream including the necessary oxygen is from the periphery toward a central hollow cylindrical region. That air stream has the function of providing the fuel cell with the necessary oxygen for the reaction within the single cells. For cooling, separator plates between the cells extend a certain distance beyond the stack periphery for removing heat from said cells to the ambient air. The passway of the hydrogen fuel is within the central region near the centres of the cells and is connected to deliver the fuel to fuel flow fields in the cells.
U.S. Pat. No. 5,470,671 describes a fuel cell configuration in which all cathode sides of the cells (single cells arranged in a line, connected in series or bicells) are located at the periphery of the cell arrangement. The cathode is the periphery of each single cell. Therefore, it is possible to dissipate all heat generated exothermically in the membrane electrode assembly to the atmosphere, and to supply the necessary reaction air stream to the membrane within the same flow path. The reaction and cooling air steam are identical. A problem resulting from the prior art configuration is a large volume that is necessary since a conventional bipolar stack configuration is not possible. Furthermore, complicated gas supply and electrical connections are necessary which generally do not allow a large number of cells which would be needed to generate high voltages. The energy densities in weight and volume, and even the efficiency of this configuration are very low.
EP 0 929 112 describes an air-cooled hydrogen air polymer electrolyte fuel cell that has a twofold channel structure cooling plate. The cooling channel structure extends through the plate from a first side to a second side of the plate, wherein the air channel structure that supplies the fuel cell with the reaction air extends from a surface of a cathode flow field into the cooling channel of the cooling plate. The cooling air stream and the reaction air steam flow cross-sectionally.
DE 196 00 200 C1 describes a fuel cell wherein one of two dry or only partially humidified reactant gases flows parallel to the temperature gradient between the reaction gas inlet and the reaction gas outlet. In addition, an air flow is used for cooling purpose.
On the other hand DE 40 28 339 A1 discloses a fuel cell system in which an excess of hydrogen is used as reaction gas and coolant simultaneously. This requires additional means of recovering none-reacted hydrogen and cycling it back through the fuel cell system what again results in high complexity and low energy densities in weight and volume.